Kate Bush and Vashti Bunyan appear to share a complete disregard for the music 'industry' and to that extent they're folk. Kate Bush only makes a record when it pleases her, which these days is many years apart, writes and produces them herself, never plays live and clearly has her home/work priorities bang in order.
VB didn't put her head above the parapet for 30 years and existed only in record completists fantasies before being bumped into public consciousness by becoming the soundtrack to a TV ad. She can hardly be said to having milked her new-found popularity since.

I have no problem with Kate Rusby who appears to be a sweet natured person with a decent voice and a nice line in lyrics. Some fans have elevated her to Yorkshire Goddess, often ladies of a certain age as far as one can tell and they are the ones who ensure her tours sell out. If she were still bashing her guitar on the minor league festival circuit more folkies would like her it's safe to say.

Kate Bush is distinct in having changed her musical concerns and styles to keep pace with her maturing as a human being while dancing to nobody's tune but her own. It's not even necessary to like much of her output to appreciate what an important musical figure she is and a model for other recording artists.